/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.transaction.annotation;

import org.springframework.transaction.TransactionDefinition;

/**
 * Enumeration that represents transaction isolation levels for use
 * with the {@link Transactional} annotation, corresponding to the
 * {@link TransactionDefinition} interface.
 *
 * @author Colin Sampaleanu
 * @author Juergen Hoeller
 * @since 1.2
 */
public enum Isolation {

    /**
     * Use the default isolation level of the underlying datastore.
     * All other levels correspond to the JDBC isolation levels.
     *
     * @see java.sql.Connection
     */
    DEFAULT(TransactionDefinition.ISOLATION_DEFAULT),

    /**
     * A constant indicating that dirty reads, non-repeatable reads and phantom reads
     * can occur. This level allows a row changed by one transaction to be read by
     * another transaction before any changes in that row have been committed
     * (a "dirty read"). If any of the changes are rolled back, the second
     * transaction will have retrieved an invalid row.
     *
     * @see java.sql.Connection#TRANSACTION_READ_UNCOMMITTED
     */
    READ_UNCOMMITTED(TransactionDefinition.ISOLATION_READ_UNCOMMITTED),

    /**
     * A constant indicating that dirty reads are prevented; non-repeatable reads
     * and phantom reads can occur. This level only prohibits a transaction
     * from reading a row with uncommitted changes in it.
     *
     * @see java.sql.Connection#TRANSACTION_READ_COMMITTED
     */
    READ_COMMITTED(TransactionDefinition.ISOLATION_READ_COMMITTED),

    /**
     * A constant indicating that dirty reads and non-repeatable reads are
     * prevented; phantom reads can occur. This level prohibits a transaction
     * from reading a row with uncommitted changes in it, and it also prohibits
     * the situation where one transaction reads a row, a second transaction
     * alters the row, and the first transaction rereads the row, getting
     * different values the second time (a "non-repeatable read").
     *
     * @see java.sql.Connection#TRANSACTION_REPEATABLE_READ
     */
    REPEATABLE_READ(TransactionDefinition.ISOLATION_REPEATABLE_READ),

    /**
     * A constant indicating that dirty reads, non-repeatable reads and phantom
     * reads are prevented. This level includes the prohibitions in
     * {@code ISOLATION_REPEATABLE_READ} and further prohibits the situation
     * where one transaction reads all rows that satisfy a {@code WHERE}
     * condition, a second transaction inserts a row that satisfies that
     * {@code WHERE} condition, and the first transaction rereads for the
     * same condition, retrieving the additional "phantom" row in the second read.
     *
     * @see java.sql.Connection#TRANSACTION_SERIALIZABLE
     */
    SERIALIZABLE(TransactionDefinition.ISOLATION_SERIALIZABLE);


    private final int value;


    Isolation(int value) {
        this.value = value;
    }

    public int value() {
        return this.value;
    }

}
